1. Field of the Invention
The present invention relates to a positive resist composition suitably usable in the production of a resist for implantation, a semiconductor integrated circuit device, a mask for integrated circuit production, a printed wiring board, a liquid crystal panel, and the like.
2. Description of the Related Art
An early chemical amplification-type positive resist composition comprising a photoacid generator and a resin protected by an acid-decomposable group is disclosed, for example, in U.S. Pat. No. 4,491,628. This chemical amplification-type positive resist composition is a pattern forming material of forming a pattern on a substrate by producing an acid in the exposed area upon irradiation with radiation such as far ultraviolet light and through a reaction using the acid as the catalyst, causing the area irradiated with actinic radiation and the area not irradiated therewith to change the solubility in a developer.
Various positive resist compositions containing a resin protected by an acid-decomposable group have been heretofore known, and for example, JP-A-5-249682 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a resist composition using a polyhydroxystyrene resin protected by an alkoxy (acetal) group, JP-A-9-211866 discloses a resist composition using a polyhydroxystyrene resin protected by two different acid-decomposable groups, JP-A-2000-352822 discloses a resist composition using a resin protected by an acetal group having a heterocyclic group at the terminal through a linking group, JP-A-2002-49156 discloses a resist composition using a polyhydroxystyrene resin protected by two different acetal groups, and JP-A-2004-246326 discloses a resist composition using a polyhydroxystyrene resin protected by an acid-decomposable group containing a group (hetero ring) having absorption at least at 248 nm.
However, in the case of using a high-reflection substrate as it is without applying an antireflection film, like the case of forming a pattern for implantation such as ion injection, the positive resist composition in general produces a strong standing wave and is demanded to be improved in this respect. Improvements are demanded also in the sensitivity and resolution.